For a variety of reasons, most of which relate to environmental and alternative energy pursuits, certain primary fuel engines, such as diesel engines, can be made to accommodate alternate fuels, such as straight vegetable oil (SVO), “biodiesel,” and other fuel oils (hereinafter “alternate fuels”). However, practical applications have demonstrated that alternate fuel should be heated up to a temperate that will allow it to easily pass through the fuel delivery system. Likewise, if left in a storage tank to cool, the alternate fuel has a tendency to increase in viscosity, congeal or solidify within fuel storage components. Thus, the alternate fuel should not be used until it has reached an appropriate temperature. As a result, these systems typically exhibit a delay required to heat the alternate fuel and must run on diesel fuel until the alternate fuel is at a usable viscosity, effectively forfeiting utilization of the alternate fuel while consuming diesel.
Recently, heating of the alternate fuel has been accomplished by co-opting a conventional fuel storage vessel and diverting a portion of engine coolant in close proximity to said storage vessel to effect heat transfer from the engine coolant. While functional, this method suffers multiple performance and efficiency limitations. As one primary example, the storage vessel and the alternate fuel therein continually loose appreciable heat energy to the surrounding atmosphere. This has the effect of rapidly promoting congealment and solidification of the alternate fuel if the engine is turned off, thereby requiring a reheat cycle and corresponding delay upon the vehicle's next use, and again the consumption of diesel fuel during this period. Also, with heat energy being continuously lost, the efficiency of the heating process itself is reduced; thus, the time required to heat is increased. In colder climates, the effect of heat energy loss worsens, heating delay increases, and the consumption of diesel fuel likewise increases. Similarly, weather phenomena such as snow or rain, or water splash upon the storage vessel, can result in heat energy loss, potentially to such degree as to overcome the heat energy provided by the diverted engine coolant, thus yielding a net decrease in alternate fuel temperature and the risk of congealment or solidification of the alternate fuel while in use.
Another performance and efficiency limitation occurs if the initial temperature of the engine coolant is lower than the initial temperature of the alternate fuel. Upon engine start and the initiation of coolant flow, the heat transfer process will instead occur in reverse, with any latent heat energy within the alternate fuel being removed by the engine coolant. The First Law of Thermodynamics dictates that any heat energy removed must again be replaced just to regain the initial alternate fuel temperature prior to cold engine start, so heating delay is further increased and the consumption of diesel fuel likewise increased.
Yet another limitation arises from the heat energy source used to control alternate fuel viscosity being the engine coolant itself, which results in the system being dependent upon running the engine on diesel or primary fuel for a period of time sufficient to heat the engine coolant before the alternate fuel becomes usable and available to the engine.
Therefore, an improved system and method of alternate fuel storage are desired.